We have demonstrated that carbon-microelectromechanical systems (C-MEMS), in which patterned photoresist is pyrolyzed in inert environment at high temperature, constitutes a powerful approach to building 3D carbon microelectrode arrays for 3D microbattery applications. High aspect ratio carbon posts (>10:1) are achieved by pyrolyzing SU-8 negative photoresist in a simple one step process. Lithium can be reversibly charged and discharged into these C-MEMS electrodes. Because of the additional volume of the posts, higher capacities are achieved with the 3D array electrodes as compared to unpatterned carbon films with the same projected electrode area. These novel electrode arrays represent one of the critical components for 3D batteries, which may be interconnected with C-MEMS leads to enable smart power management schemes. (C) 2004 The Electrochemical Society.